package com.smasher.core.other;


import android.annotation.SuppressLint;
import android.content.Context;
import android.content.SharedPreferences;
import android.provider.Settings.Secure;

import java.nio.charset.StandardCharsets;
import java.util.UUID;


public class DeviceUuidFactory {

    protected static final String PREFS_FILE = "device_id.xml";
    protected static final String PREFS_DEVICE_ID = "device_id";
    protected static UUID uuid;

    /**
     * ANDROID_ID似乎是获取Device ID的一个好选择，但它也有缺陷：在主流厂商生产的设备上，有一个很经常的bug，
     * 就是每个设备都会产生相同的 ANDROID_ID：9774d56d682e549c
     */
    public static final String BROKEN_ID = "9774d56d682e549c";

    @SuppressLint("HardwareIds")
    public DeviceUuidFactory(Context context) {
        if (uuid == null) {
            synchronized (DeviceUuidFactory.class) {
                if (uuid == null) {
                    final SharedPreferences prefs = context.getSharedPreferences(PREFS_FILE, 0);
                    final String id = prefs.getString(PREFS_DEVICE_ID, null);
                    if (id != null) {
                        // Use the ids previously computed and stored in the prefs file
                        uuid = UUID.fromString(id);
                    } else {
                        final String androidId = Secure.getString(context.getContentResolver(), Secure.ANDROID_ID);
                        // Use the Android ID unless it's broken, in which case fallback on deviceId,
                        // unless it's not available, then fallback on a random number which we store
                        // to a prefs file
                        if (!BROKEN_ID.equals(androidId)) {
                            uuid = UUID.nameUUIDFromBytes(androidId.getBytes(StandardCharsets.UTF_8));
                        } else {
                            uuid = UUID.randomUUID();
                        }
                        // Write the value out to the prefs file
                        prefs.edit().putString(PREFS_DEVICE_ID, uuid.toString()).apply();
                    }
                }
            }
        }
    }


    /**
     * Returns a unique UUID for the current android device.  As with all UUIDs, this unique ID is "very highly likely"
     * * to be unique across all Android devices.  Much more so than ANDROID_ID is.
     * *     * The UUID is generated by using ANDROID_ID as the base key if appropriate, falling back on
     * * TelephonyManager.getDeviceID() if ANDROID_ID is known to be incorrect, and finally falling back
     * * on a random UUID that's persisted to SharedPreferences if getDeviceID() does not return a
     * * usable value.
     * *     * In some rare circumstances, this ID may change.  In particular, if the device is factory reset a new device ID
     * * may be generated.  In addition, if a user upgrades their phone from certain buggy implementations of Android 2.2
     * * to a newer, non-buggy version of Android, the device ID may change.  Or, if a user uninstalls your app on
     * * a device that has neither a proper Android ID nor a Device ID, this ID may change on reinstallation.
     * *     * Note that if the code falls back on using TelephonyManager.getDeviceId(), the resulting ID will NOT
     * * change after a factory reset.  Something to be aware of.
     * *     * Works around a bug in Android 2.2 for many devices when using ANDROID_ID directly.
     * *     * @see http://code.google.com/p/android/issues/detail?id=10603
     * *     * @return a UUID that may be used to uniquely identify your device for most purposes.
     */
    public UUID getDeviceUuid() {
        return uuid;
    }


}